1. FIELD OF THE INVENTION
The present invention relates to an apparatus for observing a superconductive phenomenon caused in a superconductor.
2. DESCRIPTION OF RELATED ART
In order to observe a superconductive phenomenon caused in a superconductor such as a phenomenon on which an electric resistance of a superconductor becomes zero at a threshold temperature Tc or less, conventionally, there have been used a cryopump or cryostat for cooling the superconductor, a current power source for supplying a constant direct current to the superconductor, and a voltmeter for measuring an extremely small voltage generated therein.
Further, in order to measure the electric resistance of the superconductor when a magnetic field is applied to the superconductor, there have been used a current power source for supplying a direct current to a coil for applying a magnetic field to the superconductor, and a current controller for varying the current to be supplied to the coil so as to vary the magnetic field intensity thereof in addition to the above-mentioned apparatus. Furthermore, in order to control the current power source, the voltmeter and the current controller, and to process various kinds of electric signals, these units are connected to a microcomputer through a GPIB interface.
However, in a conventional method for observing the superconductive phenomenon on which the resistance of superconductor becomes zero at the threshold temperature Tc, and in a conventional method for measuring the variation in the electric resistance thereof when a magnetic field is applied thereto, it is necessary to separately provide a large-scaled cooling apparatus, a current power source, a voltmeter and a current controller. Furthermore, in order to control these apparatuses and to process various kinds of electric signals, it is necessary to connect these apparatuses to the microcomputer through the GPIB interface. Therefore, in the conventional method for observing the superconductive phenomenon with use of a number of apparatuses, the whole system becomes expensive, and it is difficult to use the above system, for example, for teaching the superconductive phenomenon.
Furthermore, there is provided an apparatus for observing the Meissner effect wherein a superconductor having been cooled at the temperature of the liquid nitrogen is floated above a permanent magnet for a short time.
However, since the apparatus for observing the Meissner effect which is comprised of a cooling apparatus such as the cryostat and a magnetic coil becomes large-scaled, it is difficult for ordinary people to observe the above superconductive phenomenon such as the Meissner effect easily.
Furthermore, in order to observe the superconductive phenomenon, there has been used a method for immersing the superconductive device, on which a pair of current electrodes and a pair of voltage electrodes are formed, in a coolant such as liquid nitrogen. In this method, since the temperature of the superconductive device decreases steeply, the variation in the electric resistance thereof can not be measured at respective temperatures in the range from a room temperature to the threshold temperature Tc. Also, since it is difficult to keep a thermal equilibrium state of the superconductive device, the temperature thereof can not be measured accurately.
Further, in the above-mentioned apparatus for observing the Meissner effect, since the temperature of the superconductor increases for a short time, it is impossible to keep the floatation of the superconductor caused by the Meissner effect for a long time. Furthermore, when frost adheres to the superconductor and a container for containing the superconductor upon observing the superconductive phenomenon, the light transmittance of the container decreases, resulting in that the superconductive phenomenon can not be observed clearly.